US 2006/0149250 A1 describes a bone plate having a plurality of threaded holes for receiving bone screws, said threaded holes having respective axes, which can be inclined, and a plurality of removable drill guide tips assembled in said threaded holes in alignment with said axes.
EP 1 878 394 A2 describes an orthopaedic fixation plate system comprising a fixation plate include a hole with a spherically-curved inner surface and a polyaxial bushing provided in the hole. A removable guide is provided in the polyaxial bushing. The polyaxial bushings permit the surgeon to modify the angle of each guide and bushing to a selected orientation before locking the bushing at an orientation by tightening the guide into the bushing.
As generally known, after the bone plate is on the bone and one bone anchor is inserted, it is difficult to align the remaining bone anchors to fit into the bone plate ball seat once the bone anchors are fully tightened. However, it is necessary that those bone anchors are placed exactly in the position so that once the bone anchors are tightened, the ball-shaped portion of the bone anchors lines up exactly with the ball-shaped seat in the plate. Misalignment of the ball-shaped portion of the bone anchors and the ball-shaped seat in the plate will cause stresses in the bone and it will prohibit the correct function of the plate.
It is therefore an object of the invention to provide a bone plate assembly with a guide member which is suitable for use with bone screws which are coupled polyaxially to the bone plate and which is simple and versatile in use.
This object, as well as further developments, may be solved by a bone plate assembly according to the embodiments described herein.